To achieve an improvement in efficiency in a blower, it is necessary to increase the static pressure, so that it is important that the flow in the centrifugal direction be increased in the relative flow field and that the velocity in the flow direction be reduced.
Generally speaking, in a conventional blower, to increase the flow in the centrifugal direction, it is necessary to turn the flow behind the blades into a mixed flow. In view of this, for example, JP 53-116513 A discloses a construction in which the portion of the reference line of each blade from the root to the middle portion thereof is bent at a predetermined angle of inclination in the rotating direction, and the portion of the reference line from the middle portion to the tip end portion of the blade is bent at a predetermined angle of inclination in a direction opposite to the rotating direction so that the outermost end of the reference line may be situated on the side opposite to the rotating direction with respect to the line connecting the rotation center and the above-mentioned root.
The above conventional blower is basically a so-called axial blower, in which air flows substantially along the axial direction. Thus, in its outer peripheral portion, the effect of mixed flow due to the blade profile is rather small, with the result that a sufficient increase in static pressure cannot be achieved, leading to poor ventilation efficiency, an increase in noise, etc.